Hi folks, I want to tell you that everything works fine now. I have no quick fix to post here, because it as a rather big endeavor.
The errors I had stem from migrating the old C4D R13 project upwards. A wrong linker path, a missing include path, then it compiles, but there is an illegal instruction etc. etc.
Several days of hard labor, now it works.
Thank you for your help, I will soon need more of it!
-Ingvar